Stereophonic phonograph pickup with single pad for piezoelectric element coupling, support and damping

ABSTRACT

A phonograph pickup includes a case having a top section and a bottom section. A single piece elastomer member includes a stylus beam coupler, a damping block, and two interconnecting support elements mounted in the case. A transducing element is positioned on each of the support elements, with the ends of the transducing elements inserted into apertures in the beam coupler and damping block. Electrical terminals are positioned on opposing surfaces of the transducing elements. When the top and bottom case sections are secured together, female receptacles are formed. Each female receptacle includes one of the electrical terminals positioned on the transducing elements. A guard member having a channel in its underside is secured to the housing. The guard member is positioned such that a predetermined force applied to the pickup stylus deflects the stylus carrying beam into the guard member channel.

United States Patent 3,523,690 8/1970 Vanderkoppel 274/37 3,482,061 12/1969 Grado l79/l00.4l K 2,938,966 5/1960 Spence l79/l00.4l P

Primary Examiner-Bernard Konick Assistant ExaminerRaymond F. Cardillo, Jr. AnorneyEugene W. Whitacre ABSTRACT: A phonograph pickup includes a case having a top section and a bottom section. A single piece elastomer member includes a stylus beam coupler, a damping block, and two interconnecting support elements mounted in the case. A transducing element is positioned on each of the support elements, with the ends of the transducing elements inserted into apertures in the beam coupler and damping block. Electrical terminals are positioned on opposing surfaces of the transducing elements. When the top and bottom case sections are secured together, female receptacles are formed. Each female receptacle includes one of the electrical terminals positioned on the transducing elements.

A guard member having a channel in its underside is secured to the housing. The guard member is positioned such that a predetermined force applied to the pickup stylus deflects the stylus carrying beam into the guard member channel.

PATENTED OCT 5 I97! SHEET 1 [1F 3 INVENOH MCHAEL EVANS Mmuzn FIG I A 7' TORNEY FIG 2 54 i2 78 \oz \06 \04 6 55 72 74 1c, 98 as 52 54 l: e 55 i INVENTOR M ICHAEL EVANS MlLLER v Emil y C ITTORNEY PATENTED um SE]?! 3.6 1 0,840

SHEET 3 OF 3 56 H2 34 55H0 G0 INVENTOR MiCHAEL EvANs M \LLER STEREOPI'IONIC PHONOGRAPH PICKUP WITH SINGLE PAD FOR PIEZOELECTRIC ELEMENT COUPLING, SUPPORT AND DAMPING The present invention relates to phonograph pickups, and more particularly, to an improved piezoelectric stereophonic phonograph pickup.

Stereophonic phonograph pickups generally include two mechanical to electrical transducers, one for each channel, such as piezoelectric elements, carried by a support housing which may be fastened to a phonograph tone arm. A beam member is mounted to the housing and provided at its free extremity with one or more stylus, each shaped to engage the groove of a disc record while the disc is rotated on a phonograph turntable. Means are provided in the pickup for mechanically coupling the beam member to the electrical transducers. Motion of the stylus in tracking the undulations of the disc groove is thereby communicated to the transducers which transfonn the motion into electrical signals.

The coupling means or yoke for transmitting the force from the stylus carrying beam to the electrical transducer in many stereophonic pickups is a V-shaped structure which resolves the beam motion into two 90 displaced motion components that are transmitted to two transducers. Unfortunately, such coupling means can transmit to each transducer an undesired portion of the beam motion component intended for the other of the transducers. This is due to the inherent intercoupling between the two arms of the V-shaped structure, and results in channel crosstalk. To prevent this effect, it has been necessary in the past to carefully design and assemble the pickup to minimize crosstalk between the two separate channels. Particularly, during the assembly of the pickups, it has been necessary that the transducing elements be carefully aligned with respect to each other and to other structural elements of the pickup, such as the beam member, to achieve optimum perfonnance.

A particularly troublesome problem in stereophonic pickup devices is the provision of electrical terminals for coupling the electrical output signals from the transducer elements to amplification circuitry associated with a phonograph player. In this connection, the assembly of the terminals or connectors to the transducers has been especially time consuming and therefore costly. Moreover, since the terminals usually extend beyond the pickup housing they provide a potential source of misalignment of the transducer elements which can be introduced when the pickup is mechanically coupled to the tone arm and electrically connected to the phonograph circuitry. At this time, a force may be exerted against the projecting pickup terminals and directly or indirectly coupled to the transducer elements, causing the transducer elements to move and become misaligned.

Accordingly, it is the object of the present invention to provide a simple and inexpensive pickup substantially reducing the likelihood of transducer misalignment or damage during both assembly and use.

In accordance with the present invention, a phonograph pickup includes a case having a top section and a bottom section. An elongated stylus beam is mounted to the case and includes a stylus secured near one end of the beam. The pickup utilizes two transducing elements which are mounted in an elastomer member including a stylus beam coupler, a damping block, and two support elements connecting the coupler and the block. Each transducing element is positioned on one of the elastomer member support elements, with the ends of the transducing elements inserted into apertures in the beam coupler and damping block.

In accordance with a feature of the invention, electrical terminals are positioned on opposing surfaces of the transducing elements. When the top and bottom case sections are secured together. female receptacles are formed. Each female receptacle includes one of the electrical terminals positioned on the transducing elements.

A complete understanding of the present invention may be obtained from the following detailed description thereof, when taken in conjunction with the accompanying drawing, in which:

FIG. 5 is a right side view of the stereophonic pickup yoke and transducer tenninals shown in FIG. 4;

FIG. 6 is a section view taken along the lines 6-6 in FIG. 3

with the mounting bracket, the stylus assembly, and the stylus guard, not shown; and

FIG. 7 is an exploded perspective view of the stereophonic pickup housing having the pickup yoke and tenninals seated in the lower housing section, with the pickup yoke partially broken away to show a piezoelectric transducing element and associated electrical terminal.

Referring now to the drawings wherein like reference numerals designate similar elements in the various views, a stereophonic pickup includes a substantially rectangular case or housing composed of two opposing sections of molded plastic, a top section 10 and a bottom section. 12. The top section 10 includes shoulder portions 14, I6, 18 and 20 such that the pickup may be secured to a mounting bracket 22, shown in FIGS. 2 and 3.

The casing top and bottom section 10 and 12, when assembled, define an internal cavity extending substantially the length of the casing, in which a pair of piezoelectric transducing elements 24 and 26 are housed. The bottom section 12 of the pickup case includes a rectangularly shaped opening 28 and a centrally disposed ridge 30 of triangular cross section. The ridge 30 with its projections is adapted to accurately position a stereophonic pickup yoke member 32, while the rectangular opening 28 permits a portion of the yoke member, a V- shaped beam coupler 34, to extend downward through the opening to engage the stylus carrying beam 36.

The yoke 32 is a single molded part fabricated from an elastomer material such as rubber and includes the V-shaped beam coupler 34, two support elements 38 and 40, and a damping block 42. The two support elements 38 and 40 each interconnect the V-shaped beam coupler 34 and the damping block 42. The yoke is molded to include four rectangular apertures to allow the insertion of the pickup transducing elements. Two apertures 44 and 46 are provided in the V-shaped beam coupler 34, and two apertures 48 and 50 are provided in the damping block 42.

Because the pickup yoke 32, that is, the V-shaped coupling member 34, the transducer support elements 38 and 40, and the damping block 42, is fabricated in one mold, the resulting assembly insures a precise component relationship. The transducer elements are positioned in the yoke by inserting the elements through rectangular apertures in the damping block 42, to be thereafter guided along the yoke support elements 38 and 40 until the transducer elements are inserted into the apertures in the Vshaped beam coupler 34. The transducer elements are inserted until the leading tip is flush with the front of the beam coupler 34. Thus, when the piezoelectric transducer elements 24 and 26 are inserted into the yoke 32, the transducers are quickly and accurately positioned, thereby eliminating the major cause of crosstalk.

The transducing elements 24 and 26 have a rectangular cross section and, when positioned in the yoke, their major surfaces lie in perpendicular planes with each plane disposed at an angle of 45 to a plane extending vertically through the longitudinal axis of the pickup casing. Motion of the stylus in tracking undulations of a disc recording groove, as the disc is rotated, is communicated to the transducing elements 24 and 26 through the V-shaped beam coupler 34.

The divergent legs of the beam coupler 34 are stiff axially but flexible in the direction normal to their axis. Consequently, axial forces or vibrations imparted to either of the divergent legs of the beam coupler 34 at its slotted reentrant central portion 35 (where the stylus beam is received) is transmitted to the associated transducing element. The transmitted force causes a bending of the transducing elements which convert the mechanical motions into electrical signals. Spurious resonances occurring in the pickup are damped by the damping block 42 which prevents the generation of undesired signals of substantial amplitude by the transducing elements.

Two electrical terminals are associated with each of the transducer elements 24 and 26. Thus, electrical terminals 54 and 56 are associated with transducer element 24, while electrical terminals 58 and 60 are associated with transducer 26. Each of the electrical terminal pairs are inserted into the apertures in the damping block 42 to contact opposite sides of the transducing elements. Each terminal includes a flat straight portion which contacts one side of the transducing element and a bent section adapted to cooperate with the bent section of the other of the electrical terminal pairs to form a jawlike structure. The bent portion of each electrical terminal includes a spring element. All of the .electrical terminals are identical in construction; FIG. 7 best shows the terminal con-' struction wherein the terminal 58 includes a straight flat portion 62 and a bent portion 64.

When the yoke 32 is nestled in the bottom section 12 of the pickup casing, the damping block 42 is positioned on the ridge 30 between two triangular projections 66 and 68. The triangular rail between the projections 66 and 68 mates with the inverted V-notch 70 in the bottom of the damping block 42. This accurately positions the damping block with respect to the pickup components and more particularly to the stylus assembly. Because block 42 is accurately positioned, the attached depending V-shaped coupling member 34 is likewise accurately positioned resulting in the transducing elements and stylus carrying beam 36 consistently, in mass production, assuming a predetermined spacial relationship. Consequently, the problems previously mentioned as associated with misalignment of the pickup components are eliminated.

The stylus assembly may be considered to comprise three axially aligned members: a stylus beam member 36 carrying a pair of record engaging stylus oppositely disposed near one end of the beam, a cylindrically shaped damping member 72 made of an elastomer material such as rubber, and a holder 74 which is preferably a molded plastic piece. The holder 74 includes a circular channel 76 adapted to cooperate with a recessed bearing surface 78 (FIG. 3) which captivates the holder for rotation. The holder 74 may be rotated 180 about an axis substantially parallel to the major axis of the stylus assembly. The holder 74 is manually rotated by means of a lever arm 80 which extends laterally outward from the holder extension 82, and in a plane normal to the major axis of the casing. As shown in FIG. 1', the front end of the holder 74 is provided with an axially extending dowellike projection 84 which is received in a mating bore provided in the rear portion of the damping member 72. The rear end of the stylus beam 36 is received in another or second mating bore provided in the forward or front portion of the damping member 72. The resilience of the damping member provides damping at the rear end of the stylus beam which helps damp mechanical resonances that may appear in the system during operation of the pickup. Stylus assemblies of this type are described in detail in US. Pat. No. 3,420,534.

The holder extension-82 includes two flat surfaces 86 and 88 and a rodlike extension 90. The rodlike extension 90, when the pickup is assembled, nestles in a bearing surface 92 on the underside of the bottom section 12 of the pickup casing. One of the flat surfaces 86 and 88 is urged against the underside of the bottom section 12 of the casing, when assembled, by a resilient clip 94. The clip 94 includes a central portion 96 and two perpendicularly extending legs 98 and 100. The central portion 96 includes two cars 102 and 104 which are adapted to insert into a slot 106 on an edge of the bottom section 12. When the pickup is assembled, the leg 100 is positioned over the top section with a lip 101 at the end of the leg engaging a notch 103, and the leg 98 is positioned under the holder extension 82. The clip legs 98 and thereby maintain the pickup components in proper registration. Resiliency of the clip 94 additionally provides a detent for the movement of the rotatable stylus holder 74. Desirably, the clip 94 should have sufficient resiliency to allow the legs 98 and 100 to be deflected by the holder extension 82 when rotated, yet still maintain a strong retaining force to insure both that the pickup components are maintained in registration and that the stylus holder is restrained from slipping out of the recessed bearing surface 78 during rotation between detent.

When the top and bottom sections 10 and 12 of the pickup case are secured together in complementary relationship, four female receptacles 108, 110, 112 and 114 are formed. This is best shown in FIG. 6 which is a section view of the pickup taken along the line 66 in FIG. 3 with the mounting bracket, the stylus assembly and stylus guard, not shown. Each of the female receptacles has a substantially triangular cross section. Two sides of the cross section are part of the molded plastic pickup casing while the remaining wall is one of the four electrical terminals 54, 56, 58 and 60. The spring element associated with each of the four electrical terminals protrudes into the triangular cross section to resiliently urge a male mating connector, not shown, against the molded plastic sides of the female receptacle. The male connectors form part of the circuitry adapted to couple the electrical signals produced by the transducing elements 24 and 26 to a phonograph amplifier.

Each pair of electrical terminals is spaced apart by cooperating spacers molded as part of the pickup housing sections. Thus, the electrical terminal pair 58 and 60 are spaced apart by the spacers l 16 and l 18, while the electrical terminal pair 54 and 56 are spaced apart by the spacers 122 and 124. Spacers 116 and 122 are molded as part of the bottom section 12 and spacers 1 18 and 124 are molded as part of the top section 10. Each of the spacers has a 45 sloped surface which supports one of the electrical terminals and is parallel to the sloped surface of the cooperating spacer.

During assembly, the yoke member 32 with the transducer elements and electrical terminals inserted, is positioned in the bottom section 12 of the pickup housing. The damping block 42 is inserted on the ridge 30 between the triangular projections 66 and 68, while the electrical terminals 54 and 58 are positioned on the sloped surface of the spacers 122 and 116, respectively. The portions of each electrical terminal 54 and 58 which engages the spacers sloped surface is cammed to be parallel to the surface. After positioning the yoke member and terminals in the bottom section 12, the top section 10 is thereafter positioned over the yoke member 32 and bottom section 12. The electrical terminals 56 and 60, similar to the terminals 54 and 58, are cammed such that the terminal portions engaging the sloped surface of the spacers 118 and 124 are parallel to the surface. Consequently, the spacers 118 and 124 fit between the respective terminal pairs with the sloped portion of each spacer 118 and 124 engaging its associated electrical terminal, that is, the terminals 56 and 60.

The bottom section 12 of the pickup case includes a cut out portion having two tracks 126 and 128. The tracks provide a guide for two recesses 130 and 132 in a stylus guard 134. The stylus guard 134 additionally includes a U-shaped slot 136 in its under side. When assembled, the stylus guard is positioned in the bottom case section 12, constrained by the tracks 126 and 128. The stylus guard is positioned such that when a given upward force, for example 5 grams, is applied to either stylus. to deflect the stylus carrying beam 36, the guard tips 138 and 140 bear against the record surface limiting the upward excursion of the beam. The stylus guard protects against excessive excursions of the stylus carrying beam 36 and thereby prevents damage to the stylus and an excessive force from being transmitted to the transducer elements 24 and 26 through the V-shaped beam coupler 34. The stylus guard 134 is permanently secured after adjustment in the bottom case section 12 by applying localized heat to fuse the guard and bottom section together. The localized heat may be applied by a soldering iron.

What is claimed is:

l. A phonograph pickup comprising:

a pickup case;

an elongated stylus beam mounted to said case with a stylus secured to said beam near one end thereof;

a first and a second transducing element;

an elastomer member mounted in said pickup case and including a damping block, a stylus beam coupler, and two support elements connecting said damping block and said beam coupler, said damping block and said stylus beam coupler each having an aperture adjacent each of said support elements;

said first transducing element positioned on a first one of said support elements with the ends of said transducing element inserted into the adjacent apertures in said damping block and said beam coupler; and

said second transducing element positioned on a second one of said support elements with the ends of said transducing element inserted into the adjacent apertures in said damping block and said beam coupler.

2. A phonograph pickup as defined in claim 1 wherein said pickup case includes a ridge and the underside of said damping block includes a channel such that said damping block channel and said ridge mate to accurately position said damping block within said case.,

3. A phonograph pickup as defined in claim 2 wherein said ridge includes a first projection abutting said damping block.

4. A phonograph pickup as defined in claim 3 wherein said ridge includes a second projection abutting said damping block.

5. A phonograph pickup as defined in claim 4 wherein said first and said second transducing elements have a rectangular cross section and are mounted in said elastomer member such that the major surfaces of said transducing elements lie in perpendicular planes, each plane disposed at an angle of 45 to a plane extending vertically through the longitudinal axis of said pickup case. 

1. A phonograph pickup comprising: a pickup case; an elongated stylus beam mounted to said case with a stylus secured to said beam near one end thereof; a first and a second transducing element; an elastomer member mounted in said pickup case and including a damping block, a stylus beam coupler, and two support elements connecting said damping block and said beam coupler, said damping block and said stylus beam coupler each having an aperture adjacent each of said support elements; said first transducing element positioned on a first one of said support elements with the ends of said transducing element inserted into the adjacent apertures in said damping block and said beam coupler; and said second transducing element positioned on a second one of said support elements with the ends of said transducing element inserted into the adjacent apertures in said damping block and said beam coupler.
 2. A phonograph pickup as defined in claim 1 wherein said pickup case includes a ridge and the underside of said damping block includes a channel such that said damping block channel and said ridge mate to accurately position said damping block within said case.
 3. A phonograph pickup as defined in claim 2 wherein said ridge includes a first projection abutting said damping block.
 4. A phonograph pickup as defined in claim 3 wherein said ridge includes a second projection abutting said damping block.
 5. A phonograph pickup as defined in claim 4 wherein said first and said second transducing elements have a rectangular cross section and are mounted in said elastomer member such that the major surfaces of said transducing elements lie in perpendicular planes, each plane disposed at an angle of 45* to a plane extending vertically through the longitudinal axis of said pickup case. 